This invention relates to clamping systems for Gold Dot connectors and more specifically to a shim used to apply a uniform load over the xe2x80x9cgold dotsxe2x80x9d of a Gold Dot flex circuit type of connector or other similar connectors which are being clamped by a clamping system.
A flexible connector such as a Gold Dot flex circuit 10 is a connector having a flexible sheet-like substrate 11 having a plurality of contact surfaces e.g., xe2x80x9cgold dotsxe2x80x9d 12 protruding from its surface near each end of the flex circuit as shown in FIG. 1. Each gold dot at one end is interconnected to a corresponding gold dot at the other end through traces formed within the flexible substrate. The Gold Dot flex circuit is typically used to interconnect two electronic boards. The array of gold dots at one end of the Gold Dot flex circuit make contact with an array of contact features, such as contact pads, on one electronic board while the array of gold dots at the other end of the Gold Dot flex circuit make contact with contact features, such as contact pads, at the other electronic board to be interconnected. Typically, each board and an end section of the Gold Dot flex circuit are clamped together. Specifically, a clamping system is used having a clamp member 14 into which is fitted an elastomeric pad or elastomer 16 (FIG. 2). A shield layer 18 is typically formed on the exposed surface of the elastomer. The Gold Dot flex circuit end section with the array of gold dots is placed over the elastomer 16 such that the gold dots 12 face opposite the elastomer. The electronic board 20 to be connected is then placed over the gold dots such that the contact features of the electronic board make appropriate contact with the gold dots of the Gold Dot flex circuit. A stiffener 22 is then fitted over the electronic board sandwiching the electronic board and Gold Dot flex circuit between the stiffener and the clamp member. The elastomeric pad provides compliance for urging the gold dots against the contact features on the electronic board.
To ensure proper alignment two threaded pins 24 are typically fitted in the clamp member and protrude through openings 27 in the Gold Dot flex circuit, electronic board and stiffener. Internally threaded members 26 such as nuts are then threaded on the pins to clamp the stiffener against the clamp member.
When the elastomer 16 is transferring a high load from the clamping system to the gold dots, the flexible substrate of the Gold Dot flex circuit drapes around each gold dot. A high load is the load required for causing draping of the Gold Dot flex circuit such that its substrate 11 surrounding the gold dots 12 contacts the elastomeric board, as for example shown in FIG. 3. When the elastomer is transferring a high load at under a high temperature conditions (typically over 120xc2x0 C.), the elastomer takes a set, i.e., it deforms and becomes less effective (FIG. 3). Specifically during high temperatures, the Gold Dot flex circuit flexible substrate tends to drape around the gold dots as shown in FIG. 3 and the elastomer takes a set forming depressions 27 to accommodate the gold dots 12. Consequently, the load applied by the elastomer to the gold dots is reduced since some of the load is transferred to the electronic board via the flexible substrate 11 surrounding the gold dots 12. Many times, the elastomer set causes a non-uniform load to be applied to the gold dots, i.e., the load applied to each gold dot may vary from gold dot to gold dot thus reducing the integrity of the interconnection provided by the Gold Dot flex circuit.
Some clamping systems incorporate use of elastomers having bumps for directly concentrating the force over each of the gold dots. However, even these elastomers with bumps are subject to the same problems as the regular elastomers, such as setting, when operating under a hot and/or high load conditions. Furthermore, as the density of the gold dots increases, the density of the bumps in such an elastomer must also increase. As the numbers of bumps formed on the elastomer increase so does the manufacturing difficulty as well as the manufacturing costs.
As a result of the aforementioned problems, current clamping systems utilized must be capable of applying a relatively high clamping load for ensuring that the losses due to elastomer setting or deformation will be minimized. Consequently, the components of such clamping systems must be better designed and made from more expensive materials having higher strengths so that they can absorb the higher loads to which they will be imposed. A problem, however, with applying high loads is that the elastomer, whether bumped or not, will laterally expand. Consequently, the lateral dimension of the clamping system which may be limited by the geographic location of the clamping system must be such so as to account for the expansion of the elastomer. As a result, the lateral dimension of the gold dot array is limited. Moreover, in clamping systems incorporating a bumped elastomer, expansion of the elastomer when operating under hot and/or high load conditions may cause the bumps of the elastomer to misalign from the gold dots, thereby reducing the force levels applied to the gold dots to levels that may be insufficient for insuring proper contact with the electronic board.
Thus, a need exists for providing a clamping system that overcomes all of the aforementioned problems without compromising the needed compliance of the system which is provided by the elastomer.
The present invention provides for a shim 28 (FIG. 4) between an elastomer (or other resilient material member) 16 of a clamp system and a flexible connector, as for example Gold Dot flex circuit 10, so as to focus the force from the elastomer onto the contact surfaces of the flexible connector e.g., the gold dots 12, without compromising the compliance of the overall system (FIG. 5). The shim should be of sufficient size to cover the golds dots at one end of a flexible connector. In an exemplary embodiment, a separate shim maybe incorporated at each clamp system for clamping each end of the Gold Dot flex circuit. For convenience and descriptive purposes, the inventive shim is described herein for use with a Gold Dot flex circuit. However, the inventive shim can be used with other flexible connectors which may have contact features which are not in the form of gold dots. Furthermore, for convenience and descriptive purposes, a clamp system incorporating the inventive shim is described as having an elastomer. However, it should be understood that other resilient materials instead of an elastomer may be incorporated in such clamp system.